docs: fix cypress script typo in 10-testing.mdx (#56765)

fix cypress script name typo to run `cypress:open` as declared on package.json script example

Author: dianacpg

docs/03-pages/01-building-your-application/05-optimizing/10-testing.mdx

@@ -51,7 +51,7 @@ Add Cypress to the `package.json` scripts field:
 Run Cypress for the first time to generate examples that use their recommended folder structure:
 
 ```bash filename="Terminal"
-npm run cypress
+npm run cypress:open
 ```
 
 You can look through the generated examples and the [Writing Your First Test](https://docs.cypress.io/guides/getting-started/writing-your-first-test) section of the Cypress Documentation to help you get familiar with Cypress.